'\" t
.\" Copyright (C) 2002 Andries Brouwer (aeb@cwi.nl)
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH dirfd 3 2024-05-02 "Linux man-pages 6.9.1"
.SH NAME
dirfd \- get directory stream file descriptor
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.B #include <sys/types.h>
.B #include <dirent.h>
.P
.BI "int dirfd(DIR *" dirp );
.fi
.P
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.P
.BR dirfd ():
.nf
    /* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200809L
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.fi
.SH DESCRIPTION
The function
.BR dirfd ()
returns the file descriptor associated with the directory stream
.IR dirp .
.P
This file descriptor is the one used internally by the directory stream.
As a result, it is useful only for functions which do not depend on
or alter the file position, such as
.BR fstat (2)
and
.BR fchdir (2).
It will be automatically closed when
.BR closedir (3)
is called.
.SH RETURN VALUE
On success,
.BR dirfd ()
returns a file descriptor (a nonnegative integer).
On error, \-1 is returned, and
.I errno
is set to indicate the error.
.SH ERRORS
POSIX.1-2008 specifies two errors,
neither of which is returned by the current
.\" glibc 2.8
implementation.
.TP
.B EINVAL
.I dirp
does not refer to a valid directory stream.
.TP
.B ENOTSUP
The implementation does not support the association of a file
descriptor with a directory.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.na
.nh
.BR dirfd ()
T}	Thread safety	MT-Safe
.TE
.SH STANDARDS
POSIX.1-2008.
.SH HISTORY
4.3BSD-Reno (not in 4.2BSD).
.\" It is present in libc5 (since 5.1.2) and in glibc 2.
.SH SEE ALSO
.BR open (2),
.BR openat (2),
.BR closedir (3),
.BR opendir (3),
.BR readdir (3),
.BR rewinddir (3),
.BR scandir (3),
.BR seekdir (3),
.BR telldir (3)
